1. Field of the Invention
The present invention relates to a continuously variable V-belt transmission, and more particularly to a centrifugal force compensation apparatus designed to offset the oil pressure occurring within the pulley cylinder chamber due to the centrifugal force.
2. Description of the Prior Art
There is known as a centrifugal force compensation apparatus of a continuously variable V-belt transmission, an apparatus as disclosed in U.S. Pat. No. 4,143,558, which apparatus is shown in FIG. 1. Arranged in a face-to-face relationship with an axially fixed conical disc 202 integral with a shaft 201 is an axially movable conical disc 203 mounted slidably along the shaft 201. The fixed and movable conical discs 202 and 203 define a V-shaped pulley groove in which a V-belt 204 is disposed. Within a cylinder wall 203a integral with the movable conical disc 203, a partition wall member 205 is disposed which is fixedly connected to the shaft 201 and defines a pulley cylinder chamber 206 on one side and a compensation chamber 207 on the opposite side. The cylinder chamber 206 is enclosed by the conical disc 203, cylinder wall 203a and partition wall member 205. The compensation chamber 207 is enclosed by the cylinder wall 203a, partition wall member 205 and a washer 203b fixedly attached to open end of the cylinder wall 203a. The cylinder chamber 206 and pressure compensation chamber 207 communicate with each other by an orifice 208a formed through a control member 208 slidably extending through the partition wall member 205. In the illustrated position wherein the oil pressure within the pulley cylinder chmaber 206 is low, the pulley cylinder chamber 206 is permitted to communicate with the compensation chamber 207 to supply oil to the compensation chamber 207, while, in the position illustrated by the borken lines wherein the oil pressure within the pulley cylinder chamber 206 is high, the orifice 208a is closed by the partition wall member 205. Therefore, in the case wherein the oil pressure within the pulley cylinder chamber 206 is low and the movable conical disc 203 rotates at a high speed, oil is allowed to flow into the compensation chamber 207 through the orifice 208a, so that, since the oil exists within the compensation chamber 207 as well as within the pulley cylinder chamber 206 to create substantially the same, in magnitude, oil pressure due to centrifugal forces, the oil pressures due to these centrifugal forces are offset, allowing the movable conical disc 206 to move accurately in response to the oil pressure supplied to the pulley cylinder chamber 206 even under a condition wherein the movable conical disc 206 rotates at a high speed. On the other hand, when the oil pressure within the pulley cylinder chamber 206 is high, the orifice 208a is closed to prevent the supply of oil to the compensation chamber 207, thus preventing a drop in oil pressure within the pulley cylinder chamber 206.
However, in a continuously variable transmission such centrifugal force compensation apparatus, there is a problem that since the oil pressure within the pulley cylinder chamber is released via an orifice, the pressure drops or becomes unstable owing to the variation in the volume of relief of the oil pressure. Another problem is that because there occurrs no supply of oil to the compensation chamber, the centrifugal force compensation function ceases when the oil pressure in the pulley cylinder chamber is high enough to close the orifice.